<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            /* 弹性布局，主轴和侧轴 */
            display: flex;
            /* 主轴对齐方式 */
            /* justify-content: center; */
            /* justify-content: space-between; */
            /* justify-content: space-around; */
            /* justify-content: space-evenly; */

            /* 侧轴对齐方式 */
            /* align-items: stretch; */
            /* align-items: center; */
            /* align-items: flex-start; */
            align-items: flex-end;
            /* 修改主轴方向 */
            flex-direction: column;

            height: 300px;
            border: 1px solid #000;
        }

        .box div:nth-child(2) {
            align-self: center;
        }

        .box div {
            width: 200px;
            height: 100px;
            background-color: pink;
        }
    </style>
</head>
<body>
    <div class="box">
        <div>1</div>
        <div>2</div>
        <div>3</div>
    </div>
</body>
</html>